Bookmarks and Favorites are just subsets of the same feature. At the end of the day they serve the same purpose: Help me keep tabs on the posts I take an interest in.
So I propose you unify the two a bit more, starting with the user profiles. How about cutting out “Favorites” in favor of a single “Bookmarks” tab?
Here’s a mockup of a combined view:
Post bookmarks with also-bookmarked thread parents would be displayed inline. Stand-alone post bookmarks would have a “In reply to:” prefix (at the very least). Thread bookmarks (i.e. favorites) would remain the same.
This also implies some rewording of the existing buttons, changing “Favorite” into “Bookmark Thread” with “Bookmark the entire thread” on hover for instance.